Ore mill and grinding element therefor



July 9, 1929, D. H. YOUNG ORE MILL AND GRINDING ELEMENT THEREFOR Fild Dec. 3, 1927 Thu a 77 flOfLMdf you/raj,

them of the material to be ground.

Patented July 9, 1929.

UNITED. STATES PATENT OFFICE.

DONALD H. YOUNG, F BERKELEY, CALIFORNIA, ASSIGNOR TO AMERICAN MANGANESE S TEEL'COMIPA NY, OF CHICAGQILLINOIS, A CORPORATION OF MAINE.

.=i. I 1 ORE MILL AND GRiNIJING ELEMENT THEREFOR.

Application filed December 3, 1927. Serial No. 237,347.

This invention relates to mills of the kind in which ore and other materials may be reduced to subdivided form by tumbling or otherwise agitating thematerials, usually referred to as pulp. within a container, in

the presence of. grinding elements which in:

in such a manner as to close up interstitial spaces. and prevent. the circulation among Those grinding elements which areot spherical or cylindrical form are fairly etiirient as to circulation of material to be ground, but the, area of contact between such elements is so small that there is no special tendency to further reduce larger particles in prefer- 1 cure to those particles that have already reached the desired degree of fineness.

The object of the present invention is to provide a mill of the kind described, with grinding elements which While favoring tree circulation of the pulp during the reduction process, will act more selectively upon the larger pieces and less upon the particles that have reached the desired degree of fineness, and thereby avoid the condition of sliming to a much greater degree than when using grinding elements of design heretofore known; and the invention proceeds upon the principle of constructing grinding elements for use in a mill of the kind described, with substantially plane faces, as distinguished from spheroidal or cylindrical faces and with their said plane faces inclined to their bases and meeting at angles which are very materially less than a right angle, so that the elements are not comple1nentary,and while exercising their superior reduction effeet, cannot pack solid and prevent free cir culation of the pulp. I have obtained good results by designing the grinding elements in the. form of pyramids of polygonal section. and particularly tetrahedrons, or p vramids oftriangular section; the base of each pyramid being exposed as one of the grinding faces.

In order that the invention may be fully understood, an illustrative embodiment thereof is shown in the accompanying drawing, in which- Figure 1 is a transverse section of a container in the form of a. rotary cylinder, into which pieces of ore or other mineral are introduced for the pupose of reduction to subdivided form by the physical process of attrition.

Figure 2 is aperspective view showing the preferred form of grinding element.

Figure 3 is a section in a plane indicated by the line 3"3" of Figure 2.

Figure 4 is a section in a plane indicated by the line 4"4" of Figure 3.

1 represents a rotary cylinder or other tumbling container for mineral substances such as ore (indicated generally at X) and 2 represents grinding elements introduced into and distributed throughout the mass of material X in the cylinder 1 to assist in reducing the material as the latter is tumbled and agitated within the cylinder. Instead of having s' heroidal,-cylindrical, or even cubical grin ing elements as heretofore used or proposed, the grinding elements 2 are designed as polyhedrons, and particularly tetrahedrons or equi-lateral triangular pyramids, as more clearly shown in Figures 2, 3, and 4. Grinding elements constructed on the principle 'hereinbefore set forth, and used in a tumbling mill, not only present fiat grinding faces to the material to be ground, but they are in such a state of instability, When masscdwith the material to be ground, that they greatly promote, among the elements, the relative movements depended u on for grinding action, and open- 1ng up 0 the interstitial spaces to the entry of the larger particles and causing these to be acted upon in preference to particles that have already attained sufiicient degree of reduction.

An important feature of the present invention and one that contributes largely to the instabilit of the grinding elements above IGfQX'IGt to is the absence of parallelism between any two faces of an element.

Grinding elements constructed in the forms of tetrahetlrons have the advantage of in! parking together and excluding the pulp, since their angles are notcomplementary in the sense that a space defined by adjacentfares on two grindin element-s cannot be filled by a third grinding clement. Consequently, there will be free circulation of the material and tumbling of the grinding elements at all times.

In additioxr to serving with great efficiency when used in a tumbling mill, the grinding element of the present invention lends itself I with especial advantage to the production of the elements by the process of casting,

are substantially plane-and triangular in form, and related onetoanother at angles materially less than'a right angle.'

2. In a tumbling mill, in combination, a container, and grinding elements in said container, each of which is constructed in the form of a tetrahedron having faces that are substantially plane and triangular in form. 3. Grinding elements for tumbling mills,

- comprising polyhedrons each having triangular faces and constructed with a plurality of the angles included between its meeting faces; less than a right angle.

4. Grinding elementsfor tumbling mills, comprising .polyhedrons each having triangular faces and constructed with a majority of theangles included between its-meeting faces, less than a right angle.

5. Grinding elements for tumbling mills,

comprising polyhedrons each having triangular faces, and constructed with substantially all of. the included angles between its meeting faces less than a right angle.

6. Grinding elements for tumbling mill, comprising bodies in the form of pyramids with triangular sides and having their bases 25 well as their sides exposed as grinding aces.

having the shape of tetrahedrons' 8. Grinding elements for tumbling mills, having substantially the shape of regular tetrahedrons.

9. Grinding'elements for tumbling mills, having the shape of three-sided pyramids.

10. Grinding elements for tumbling mills, each comprising a polyhedron having substantially all of its adjacent faces at an acute angle to each other.

'11. Grinding elements for tumbling mills, provided with acute angular edges and triangular crushing surfaces.

7. Grinding elements for tumbling mills,

12. Balanced grinding elements for tulnbling mills, provided with substantially plane triangular crushing surfaces and interposed acute angular edges.

13. Universally balanced grinding elements for tumbling mills,- provided each with similar triangular substantially plane crushing faces dis osed-at an acute angle each to the others, a ong their meeting edges.

Signed at Oakland, California, this 7th day of Nov., 1927.

DONALD H. YOUNG. 

